Number of length n+1 0..2 arrays with at most one downstep in every n consecutive neighbor pairs.

Terms

a(0) =9a(1) =26a(2) =66a(3) =147a(4) =294a(5) =540a(6) =927a(7) =1507a(8) =2343a(9) =3510a(10) =5096a(11) =7203a(12) =9948a(13) =13464a(14) =17901a(15) =23427a(16) =30229a(17) =38514a(18) =48510a(19) =60467a(20) =74658a(21) =91380a(22) =110955a(23) =133731a(24) =160083a(25) =190414a(26) =225156a(27) =264771a(28) =309752a(29) =360624